Hey there! I bought this cave (http://www.petsmart.com/product/inde...AvailInUS%2FNo) that's made of plastic for my betta, and I think it would look awesome with moss all over it! Would the moss be able to grow on it? Also how would I "attach" the moss to it? Thanks!

Marimo moss tends to grow in balls rather than on surfaces. For a cave like this I would suggest java moss, or if you have high enough lighting weeping moss, pearl moss, or flame moss. To attach the moss you can either tie it down with sewing thread directly onto the cave, or tie it down to a wire mesh (be sure to buy one made for aquarium moss) and attach the mesh to the cave.